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The Remarkable Mid-Infrared Jet of the Massive Young Stellar Object G35.20-0.74
The young massive stellar object G35.20-0.74 was observed in themid-infrared using T-ReCS on Gemini South. Previous observations haveshown that the near-infrared emission has a fanlike morphology that isconsistent with emission from the northern lobe of a bipolar radio jetknown to be associated with this source. Mid-infrared observationspresented in this Letter show a monopolar jet-like morphology as well,and it is argued that the mid-infrared emission observed is dominated bythermal continuum emission from dust. The mid-infrared emission nearestthe central stellar source is believed to be directly heated dust on thewalls of the outflow cavity. The hydroxyl, water, and methanol masersassociated with G35.20-0.74 are spatially located along thesemid-infrared cavity walls. Narrow jet or outflow cavities such as thismay also be the locations of the linear distribution of methanol masersthat are found in association with massive young stellar objects. Thefact that G35.20-0.74 has mid-infrared emission that is dominated by theoutflow, rather than disk emission, is a caution to those who considermid-infrared emission from young stellar objects to come only fromcircumstellar disks.
| Precise radial velocities of giant stars. I. Stable stars
Context: .Future astrometric missions such as SIM PlanetQuest need verystable reference stars. K giants have large luminosities, which placethem at large distances and thus the jitter of their photocenters bycompanions is relatively small. Therefore K giants would be best suitedas references. To confirm this observationally a radial velocity surveyis performed to quantify the level of intrinsic variability in Kgiants. Aims: .From this radial velocity survey we present 34 Kgiants with an observed standard deviation of the radial velocity ofless than 20 m/s. These stars are considered "stable" and can be used asradial velocity standards. Methods: .The radial velocity surveycontains 179 K giants. All K giants have a declination between -30°and +65° and visual magnitude of 3{-}6 mag. The CoudéAuxiliary Telescope (CAT) at UCO/Lick Observatory is used to obtainradial velocities with an accuracy of 5{-}8 m/s. The number of epochsfor the 34 stable stars ranges from 11 to 28 with a total timespan ofthe observations between 1800 and a little over 2200 days. Results: .The observational results of the 34 "stable" stars are showntogether with a discussion about their position in the MV vs.B-V diagram and some conclusions concerning the radial velocityvariability of K giants. These results are in agreement with thetheoretical predictions. K giants in a certain range of theMV vs. B-V diagram are suitable reference stars.
| A historic jet-emission minimum reveals hidden spectral features in 3C 273
Aims. The aim of this work is to identify and study spectral features inthe quasar 3C 273 usually blended by its strong jet emission. Methods: . A historic minimum in the sub-millimetre emission of 3C 273triggered coordinated multi-wavelength observations in June 2004. X-rayobservations from the INTEGRAL, XMM-Newton and RXTE satellites arecomplemented by ground-based optical, infrared, millimetre and radioobservations. The overall spectrum is used to model the infrared andX-ray spectral components. Results: . Three thermal dust emissioncomponents are identified in the infrared. The dust emission on scalesfrom 1 pc to several kpc is comparable to that of other quasars, asexpected by AGN unification schemes. The observed weakness of the X-rayemission supports the hypothesis of a synchrotron self-Compton originfor the jet component. There is a clear soft-excess and we find evidencefor a very broad iron line which could be emitted in a disk around aKerr black hole. Other signatures of a Seyfert-like X-ray component arenot detected. Conclusions: .
| Integrated optics for astronomical interferometry. VI. Coupling the light of the VLTI in K band
Aims. Our objective is to prove that integrated optics (IO) is not onlya good concept for astronomical interferometry but also a workingtechnique with high performance. Methods: . We used thecommissioning data obtained with the dedicated K-band integrated opticstwo-telescope beam combiner that now replaces the fiber coupler MONA inthe VLTI/VINCI instrument. We characterize the behavior of this IOdevice and compare its properties to other single mode beam combinerlike the previously used MONA fiber coupler. Results: . The IOcombiner provides a high optical throughput, a contrast of 89% with anight-to-night stability of a few percent. Even if a dispersive phase ispresent, we show that it does not bias the measured Fourier visibilityestimate. An upper limit of 5×10-3 for the cross-talkbetween linear polarization states has been measured. We take advantageof the intrinsic contrast stability to test a new astronomical procedurefor calibrating diameters of simple stars by simultaneously fitting theinstrumental contrast and the apparent stellar diameters. This methodreaches an accuracy with diameter errors on the order of previous onesbut without the need of an already known calibrator. Conclusions:. These results are an important step for IO, since they prove itsmaturity in an astronomical band where the technology has been speciallydeveloped for astronomical convenience. It paves the way to incomingimaging interferometer projects.
| Atlas and Catalog of Dark Clouds Based on Digitized Sky Survey I
We present a quantitative atlas and catalog of dark clouds derived byusing the optical database ``Digitized Sky Survey I''. Applying atraditional star-count technique to 1043 plates contained in thedatabase, we produced an AV map covering the entire region inthe galactic latitude range |b| ≤ 40°. The map was drawn at twodifferent angular resolutions of 6' and 18', and is shown in detail in aseries of figures in this paper. Based on the AV map, weidentified 2448 dark clouds and 2841 clumps located inside them. Somephysical parameters, such as the position, extent, and opticalextinction, were measured for each of the clouds and clumps. We alsosearched for counterparts among already known dark clouds in theliterature. The catalog of dark clouds presented in this paper lists thecloud parameters as well as the counterparts.
| Observations of Stellar Maser Sources with No IRAS Counterpart
We investigated stellar maser sources with no IRAS counterpart at theradio, middle-infrared, and near-infrared wavelengths. A 43GHz SiO masersearch for 120 2MASS/MSX objects, and 10 OH 1612MHz sources with no or avery faint MSX counterpart, resulted in 43 SiO detections: one OH1612MHz source, 2 near-infrared stars, and 40 MSX sources. Additionalnear-infrared J-, H-, and K-band observations of the OH 1612MHz sourcesdetected 5 near-infrared counterparts. Furthermore, middle-infraredimaging observations at 8.8, 9.7, 12.4, and 24.5μm with the Subaru8.2-m telescope found counterparts for 2 near-infrared stars with SiOmasers, and counterparts for 6 OH 1612MHz sources. However, 4 OH 1612MHzsources were not detected in the sensitive near- and middle-infraredsearches; three of these are relatively strong OH maser sources forwhich the positions were known accurately. We conclude that one of these(OH 028.286i‑01.801) must be a young object in a star-formingregion.
| Deepsky delights.
Not Available
| The epoch of the constellations on the Farnese Atlas and their origin in Hipparchus's lost catalogue
Not Available
| Observations and Modeling of the 2-25 μm Emission from High-Mass Protostellar Object Candidates
This is a report on detailed modeling of young high-mass protostellarcandidates during their most embedded and obscured phases. We performednarrowband mid-infrared imaging of three candidate high-massprotostellar objects in G11.94-0.62, G29.96-0.02, and G45.07+0.13 atGemini Observatory using the Thermal-Region Camera and Spectrograph(T-ReCS). The sources were imaged through up to 11 narrowband filters,sampling their SEDs over the entire 2-25 μm infrared range. For thefirst time, we have fit the observed SEDs of massive protostars withmodels that take into account departures from spherical symmetry in theinfalling envelopes. In this way, we have been able to derive from themodels the detailed physical parameters for these earliest stages ofmassive stellar life. Our detailed modeling suggests that massive starformation can proceed in a way very similar to the formation of low-massstars.
| Broad-band photometric colors and effective temperature calibrations for late-type giants. I. Z = 0.02
We present new synthetic broad-band photometric colors for late-typegiants based on synthetic spectra calculated with the PHOENIX modelatmosphere code. The grid covers effective temperatures T_eff=3000dots5000 K, gravities log g=-0.5dots{+3.5}, and metallicities[M/H]=+0.5dots{-4.0}. We show that individual broad-band photometriccolors are strongly affected by model parameters such as molecularopacities, gravity, microturbulent velocity, and stellar mass. Ourexploratory 3D modeling of a prototypical late-type giant shows thatconvection has a noticeable effect on the photometric colors too, as italters significantly both the vertical and horizontal thermal structuresin the outer atmosphere. The differences between colors calculated withfull 3D hydrodynamical and 1D model atmospheres are significant (e.g.,Δ(V-K)0.2 mag), translating into offsets in effectivetemperature of up to 70 K. For a sample of 74 late-type giants in theSolar neighborhood, with interferometric effective temperatures andbroad-band photometry available in the literature, we compare observedcolors with a new PHOENIX grid of synthetic photometric colors, as wellas with photometric colors calculated with the MARCS and ATLAS modelatmosphere codes. We find good agreement of the new synthetic colorswith observations and published T_eff-color and color-color relations,especially in the T_eff-(V-K), T_eff-(J-K) and (J-K)-(V-K) planes.Deviations from the observed trends in the T_eff-color planes aregenerally within ±100 K for T_eff=3500 to 4800 K. Syntheticcolors calculated with different stellar atmosphere models agree to±100 K, within a large range of effective temperatures andgravities. The comparison of the observed and synthetic spectra oflate-type giants shows that discrepancies result from the differencesboth in the strengths of various spectral lines/bands (especially thoseof molecular bands, such as TiO, H2O, CO) and the continuum level.Finally, we derive several new T_eff-log g-color relations for late-typegiants at solar-metallicity (valid for T_eff=3500 to 4800 K), based bothon the observed effective temperatures and colors of the nearby giants,and synthetic colors produced with PHOENIX, MARCS and ATLAS modelatmospheres.
| First results from the ESO VLTI calibrators program
The ESO Very Large Telescope Interferometer (VLTI) is one of the leadinginterferometric facilities. It is equipped with several 8.2 and 1.8 mtelescopes, a large number of baselines up to 200 m, and with severalsubsystems designed to enable high quality measurements and to improvesignificantly the limits of sensitivities currently available tolong-baseline interferometry. The full scientific potential of the VLTIcan be exploited only if a consistent set of good quality calibrators isavailable. For this, a large number of observations of potentialcalibrators have been obtained during the commissioning phase of theVLTI. These data are publicly available. We briefly describe theinterferometer, the VINCI instrument used for the observations, the dataflow from acquisition to processed results, and we present and commenton the volume of observations gathered and scrutinized. The result is alist of 191 calibrator candidates, for which a total of 12 066observations can be deemed of satisfactory quality. We present a generalstatistical analysis of this sample, using as a starting point theangular diameters previously available in the literature. We derive thegeneral characteristics of the VLTI transfer function, and its trendwith time in the period 2001 through mid-2004. A second paper will bedevoted to a detailed investigation of a selected sample, aimed atestablishing a VLTI-based homogeneous system of calibrators.
| CHARM2: An updated Catalog of High Angular Resolution Measurements
We present an update of the Catalog of High Angular ResolutionMeasurements (CHARM, Richichi & Percheron \cite{CHARM}, A&A,386, 492), which includes results available until July 2004. CHARM2 is acompilation of direct measurements by high angular resolution methods,as well as indirect estimates of stellar diameters. Its main goal is toprovide a reference list of sources which can be used for calibrationand verification observations with long-baseline optical and near-IRinterferometers. Single and binary stars are included, as are complexobjects from circumstellar shells to extragalactic sources. The presentupdate provides an increase of almost a factor of two over the previousedition. Additionally, it includes several corrections and improvements,as well as a cross-check with the valuable public release observationsof the ESO Very Large Telescope Interferometer (VLTI). A total of 8231entries for 3238 unique sources are now present in CHARM2. Thisrepresents an increase of a factor of 3.4 and 2.0, respectively, overthe contents of the previous version of CHARM.The catalog is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/431/773
| The G9.62+0.19-F hot molecular core. The infrared view on very young massive stars
We present the results of an extensive infrared study of the massivestar-forming region G9.62+0.19. The data cover information from broad-and narrow-band filters in the wavelength range from 1 to 19 μm andare obtained with ESO's near- and thermal infrared camera ISAAC at theVLT and with the mid-infrared cameras TIMMI2 (La Silla, ESO) andSpectroCam-10 (Mt. Palomar). The high sensitivity and resolutionprovided by these facilities revealed intriguing new details of thisstar-forming region, especially of the embedded hot molecular core (HMC)-- component F. We analyse the newly found infrared sub-structure offour objects in this HMC region. While one of these objects (F2) isprobably a foreground field star, the nature of the brightest object inthe near-infrared there (F1) remains somewhat enigmatic. Our newastrometry proves that this object is not coincident with the peak ofthe molecular line emission of the HMC, but displaced by 1.7arcsecs which translates to nearly 10,000 AU on a linear scale. On thebasis of the available data we estimate this object to be an additionalembedded object with a dense dust shell. Very near the HMC location wefind L' band emission which strongly rises in flux towards longerwavelengths. We presume that this emission (F4) arises from the envelopeof the HMC which is known to be associated with a molecular outflowroughly aligned along the line of sight. Thus, the clearing effect ofthis outflow causes strong deviations from spherical symmetry whichmight allow infrared emission from the HMC to escape through the outflowcavities. This presents the first direct detection of an HMC at awavelength as short as 3.8 μm. At 11.7 μm and 18.75 μm, the HMCcounterpart F4 ultimately proves to be the most luminous IR sourcewithin the G9.62+0.19-F region. In addition, within the entireG9.62+0.19 complex our narrow-band data and the K band imagingpolarimetry reveal well-defined regions of enhanced Brγ andH2 emission as well as a sector where a large contributioncomes from scattered light. Combining our results with high-resolutionradio data we make predictions about the extinction within thisstar-forming region which clarifies why some of the associatedultracompact H II regions are not visible in the near-infrared. Ourinvestigations show the complexity of massive star formation in its fullgrandeur, but they also demonstrate that the related problems can betackled by observations using the new generation of infrared cameras.Based on observations made with the ESO VLT at the Paranal Observatoryunder programme IDs 63.I-0329 and 67.C-0264 and with ESO'S TIMMI2 on LaSilla under programme ID 71.C-0438.All appendices are only available in electronic form athttp://www.edpsciences.org
| Stellar Photometry Using Old Photographic Plates
The precision of various methods of stellar photometry on oldphotographic plates is investigated using the original plates or theirdigitized copies from the plate collection of the Maria MitchellObservatory (MMO), It is shown, in particular, that the simple and fastmethod of eye photometry is comparable in precision to the traditional"objective" methods using a microphotometer to measure the plates ofimage analysis software to measure digital copies of small parts of theplates obtained with a CCD camera. All these methods provide photometricaccuracy of +/-0.1-0.2 magnitude on the MMO plates. It is demonstratedthat the high-performance commercially available scanner AgfaScan T5000used for plate digitization at the MMO produces images that can bemeasured to a considerably higher precision of +/-0.05 magnitude, whichis sufficient for most purposes of photographic stellar photometry. Theresults of this investigation may be of interest to those who use oldplates for stellar photometry, as well as to those who look for anadequate, fast, and relatively inexpensive scanner to digitize theirplate archive.
| High-Resolution Imaging of Dust Shells by Using Keck Aperture Masking and the IOTA Interferometer
We present first results of an experiment to combine data from Keckaperture masking and the Infrared-Optical Telescope Array to image thecircumstellar environments of evolved stars with ~20 mas resolution. Theunique combination of excellent Fourier coverage at short baselines andhigh-quality long-baseline fringe data allows us to determine thelocation and clumpiness of the innermost hot dust in the envelopes andto measure the diameters of the underlying stars themselves. We findevidence for large-scale inhomogeneities in some dust shells and alsosignificant deviations from uniform brightness for the photospheres ofthe most evolved M stars. Deviations from spherically symmetric massloss in the red supergiant NML Cyg could be related to recent evidencefor dynamically important magnetic fields and/or stellar rotation. Wepoint out that dust shell asymmetries, like those observed here, canqualitatively explain the difficulty recent workers have had insimultaneously fitting the broadband spectral energy distributions andhigh-resolution spatial information, without invoking unusual dustproperties or multiple distinct shells (from hypothetical``superwinds''). This paper is the first to combine opticalinterferometry data from multiple facilities for imaging, and we discussthe challenges and potential for the future of this method, givencurrent calibration and software limitations.
| Polycyclic Aromatic Hydrocarbons and Crystalline Silicates in the Bipolar Post-Asymptotic Giant Branch Star IRAS 16279-4757
IRAS 16279-4757 belongs to a group of post-asymptotic giant branch(post-AGB) stars showing both polycyclic aromatic hydrocarbon (PAH)bands and crystalline silicates. We present mid-infrared images thatresolve the object for the first time. The morphology is similar to thatof the ``Red Rectangle'' (HD 44179), the prototype object with PAHs andcrystalline silicates. A two-component model and images suggest a denseoxygen-rich torus, an inner, low-density, carbon-rich region, and acarbon-rich bipolar outflow. The PAH bands are enhanced at the outflow,while the continuum emission is concentrated toward the center. Ourfindings support the suggestion that mixed chemistry and morphology areclosely related. We discuss the Infrared Space ObservatoryShort-Wavelength Spectrometer (ISO SWS) spectra of IRAS 16279-4757.Several bands in the ISO SWS spectrum show a match with anorthite: thiswould be the first detection of this mineral outside the solar system.Compared to HD 44179, the shapes of PAH bands are closer to those ofplanetary nebulae, possibly related to a population of small PAHspresent in HD 44179 but absent around IRAS 16279-4757. Detailedexamination of the spectra shows the individual character of these twoobjects. The comparison suggests that the torus found in IRAS 16279-4757may have formed more recently than that in HD 44179.Based on observations with the European Southern Observatory 3.6 mtelescope with TIMMI-2 at La Silla. The proposal number is 71.D-0049.Based on observations with ISO, an ESA project with instruments fundedby ESA Member States (especially the PI countries: France, Germany, theNetherlands, and the United Kingdom) with the participation of theInstitute of Space and Astronautical Science (ISAS, Japan) and NASA.
| The hot core-ultracompact H II connection in G10.47+0.03
We present infrared imaging and spectroscopic data of the complexmassive star-forming region G10.47+0.03. The detection of sevenmid-infrared (MIR) sources in our field combined with a sensitiveKs/ISAAC image allows to establish a very accurate astrometry, at thelevel of 0.3 arcsec. Two MIR sources are found to be coincident with twoultracompact H II regions (UCH II s) within our astrometric accuracy.Another MIR source lies very close to three other UCH II regions and tothe hot molecular core (HMC) in G10.47+0.03. Spectroscopy of two of themost interesting MIR sources allows to identify the location andspectral type of the ionizing sources. We discuss in detail therelationship between the HMC, the UCH II regions and the nearby MIRsource. The nature of the other MIR sources is also investigated.Based on observations collected at the European Southern Observatory, LaSilla, Chile. Prop.ID:67.C-0359(A) and Prop.ID:69.C-0189(A).
| First observations with an H-band integrated optics beam combiner at the VLTI
This paper reports results obtained with the Very Large TelescopeInterferometer Commissioning Instrument (VLTI-VINCI) where the fiberinterferometric coupler MONA was temporarily replaced by an integratedoptics beam combiner (IONIC). The two-beam combiner operating in the Hatmospheric band was tested at Paranal during two weeks in July 2002.Fringes were recorded on several stars with the siderostats and the UnitTelescopes (UT). We demonstrate that integrated optics allows beamcombination with a high interferometric efficiency, stability andspatial filtering. The instrumental visibility of VLTI+IONIC is betterthan 85%, which is just 5% under the visibility of the IONIC devicealone. During this run, the flux injection in the IONIC combiner was notoptimized since we used the K-band MONA optics. However, we obtainfringes with the 35 cm siderostats on a star of magnitude mH=2.47(κ2 Scl). It allows us to extrapolate a magnitudearound mH6 with 8 m telescopes without adaptive optics and in thesame poor injection conditions.Based on observations collected at the European Southern Observatory,Paranal, Chile (public commissioning data).
| Mid-infrared emission of galactic nuclei. TIMMI2 versus ISO observations and models
We investigate the mid-infrared radiation of galaxies that are poweredby a starburst or by an AGN. For this end, we compare the spectraobtained at different spatial scales in a sample of infrared brightgalaxies. ISO observations which include emission of the nucleus as wellas most of the host galaxy are compared with TIMMI2 spectra of thenuclear region. We find that ISO spectra are generally dominated bystrong PAH bands. However, this is no longer true when inspecting themid-infrared emission of the pure nucleus. Here PAH emission is detectedin starbursts whereas it is significantly reduced or completely absentin AGNs. A physical explanation of these new observational results ispresented by examining the temperature fluctuation of a PAH afterinteraction with a photon. It turns out that the hardness of theradiation field is a key parameter for quantifying the photo-destructionof small grains. Our theoretical study predicts PAH evaporation in softX-ray environments. Radiative transfer calculations of clumpy starburstsand AGN corroborate the observational fact that PAH emission isconnected to starburst activity whereas PAHs are destroyed near an AGN.The radiative transfer models predict for starbursts a much largermid-infrared size than for AGN. This is confirmed by our TIMMI2acquisition images: We find that the mid-infrared emission of Seyfertsis dominated by a compact core while most of the starbursts arespatially resolved.Based on ESO: 68.B-0066(A) and observations with ISO, an ESA projectwith instruments funded by ESA Member States (especially the PIcountries: France, Germany, The Netherlands and the UK) with theparticipation of ISAS and NASA.}
| Mid-IR spectroscopy of T Tauri stars in Chamealeon I: Evidence for processed dust at the earliest stages
We present mid-IR spectroscopy of three T Tauri stars in the youngChamealeon I dark cloud obtained with TIMMI2 on the ESO 3.6 m telescope.In these three stars, the silicate emission band at 9.7 mu m isprominent. We model it with a mixture of amorphous olivine grains ofdifferent size, crystalline silicates and silica. The fractional mass ofthese various components change widely from star to star. While thespectrum of CR Cha is dominated by small amorphous silicates, in VW Cha(and in a lesser degree in Glass I), there is clear evidence of a largeamount of processed dust in the form of crystalline silicates and largeamorphous grains. This is the first time that processed dust has beendetetected in very young T Tauri stars ( ~ 1 Myr).
| The evolution of V4334 Sgr (Sakurai's object) in the Mid-Infrared
Since Sakurai's object (V4334 Sgr) underwent a late helium flash in1995, its fast evolution has been monitored with great effort. Wepresent TIMMI and TIMMI 2 photometric observations covering a spectralrange from 5 to 20 μ m with a total of 8 filters. We found drasticchanges in the spectral energy distribution indicating a drop oftemperature in the dust envelope from 1000 to 600 K in half a year only.Combined with optical observations reported elsewhere, we conclude thatthe phase of dust formation has probably stopped in mid-2001 and thatthe dusty envelope has been expanding only, ever since. An expansionvelocity of about 1000 km s-1 is required to explain therapid cooling. Other optical and near-infrared observations support theexistence of such high velocity flows in the envelope of V4334 Sgr. Anestimate for the bolometric luminosity of ~2000 L_sun is derived for adistance of 1 kpc. Taking into account theoretical models a distance of2 +/- 1 kpc to V4334 Sgr is suggested. As a consequence of its fastfinal helium flash evolution, Sakurai's object may start to destroy itssurrounding dust in the not too distant future.Based on observations collected at the European Southern Observatory,Chile, proposals 65.L-0702, 67.D-0413, 68.D-0542.
| The radii and spectra of the nearest stars
We discuss direct measurements of the radii of 36 stars located closerthan 25 parsecs to the Sun. We present the data on 307 radii and 326spectral types and luminosity classes for the nearest stars locatedinside the sphere with a radius of 10 parsecs.
| A Disrupted Circumstellar Torus inside η Carinae's Homunculus Nebula
We present thermal infrared images of the bipolar nebula surroundingη Carinae at six wavelengths from 4.8 to 24.5 μm. These wereobtained with the MIRAC3 camera system at the Magellan Observatory. Ourimages reveal new intricate structure in the bright core of the nebula,allowing us to reevaluate interpretations of morphology seen in imageswith lower resolution. Complex structures in the core might not arisefrom a pair of overlapping rings or a cool (110 K) and very massive dusttorus, as has been suggested recently. Instead, it seems more likelythat the arcs and compact knots comprise a warm (200-350 K) disruptedtorus at the intersection of the larger polar lobes. Some of the arcsappear to break out of the inner core region and may be associated withequatorial features seen in optical images. The torus could have beendisrupted by a posteruption stellar wind or by ejecta from the GreatEruption itself if the torus existed before that event. Kinematic dataare required to rule out either possibility. Based on observations madeat the Baade telescope of the Magellan Observatory, a joint facility ofthe Carnegie Observatories, Harvard University, Massachusetts Instituteof Technology, University of Arizona, and University of Michigan.
| The mineral composition and spatial distribution of the dust ejecta of NGC 6302
We have analysed the full ISO spectrum of the planetary nebulaNGC 6302 in order to derive the mineralogicalcomposition of the dust in the nebula. We use an optically thin dustmodel in combination with laboratory measurements of cosmic dustanalogues. We find two main temperature components at about 100 and 50 Krespectively, with distinctly different dust compositions. The warmcomponent contains an important contribution from dust without stronginfrared resonances. In particular the presence of small warm amorphoussilicate grains can be excluded. The detection of weak PAH bands alsopoints to a peculiar chemical composition of the dust in thisoxygen-rich nebula. The cool dust component contains the bulk of themass and shows strong emission from crystalline silicates, which containabout 10 percent of the mass. In addition, we identify the 92 mu m bandwith the mineral calcite, and argue that the 60 mu m band contains acontribution from the carbonate dolomite. We present the mass absorptioncoefficients of six different carbonate minerals. The geometry of thedust shell around NGC 6302 is studied withmid-infrared images obtained with TIMMI2. We argue that the cool dustcomponent is present in a circumstellar dust torus, while the diffuseemission from the warm component originates from the lobes. Based onobservations with ISO, an ESA project with instruments funded by ESAMember States (especially the PI countries: France, Germany, TheNetherlands and the UK) and with the participation of ISAS and NASA.Based on observations made with ESO Telescopes at the La Silla orParanal Observatories under programme ID 67.D-0132(A).
| A catalogue of calibrator stars for long baseline stellar interferometry
Long baseline stellar interferometry shares with other techniques theneed for calibrator stars in order to correct for instrumental andatmospheric effects. We present a catalogue of 374 stars carefullyselected to be used for that purpose in the near infrared. Owing toseveral convergent criteria with the work of Cohen et al.(\cite{cohen99}), this catalogue is in essence a subset of theirself-consistent all-sky network of spectro-photometric calibrator stars.For every star, we provide the angular limb-darkened diameter, uniformdisc angular diameters in the J, H and K bands, the Johnson photometryand other useful parameters. Most stars are type III giants withspectral types K or M0, magnitudes V=3-7 and K=0-3. Their angularlimb-darkened diameters range from 1 to 3 mas with a median uncertaintyas low as 1.2%. The median distance from a given point on the sky to theclosest reference is 5.2degr , whereas this distance never exceeds16.4degr for any celestial location. The catalogue is only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/183
| CHARM: A Catalog of High Angular Resolution Measurements
The Catalog of High Angular Resolution Measurements (CHARM) includesmost of the measurements obtained by the techniques of lunaroccultations and long-baseline interferometry at visual and infraredwavelengths, which have appeared in the literature or have otherwisebeen made public until mid-2001. A total of 2432 measurements of 1625sources are included, along with extensive auxiliary information. Inparticular, visual and infrared photometry is included for almost allthe sources. This has been partly extracted from currently availablecatalogs, and partly obtained specifically for CHARM. The main aim is toprovide a compilation of sources which could be used as calibrators orfor science verification purposes by the new generation of largeground-based facilities such as the ESO Very Large Interferometer andthe Keck Interferometer. The Catalog is available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/386/492, and from theauthors on CD-Rom.
| High mass Class I sources in M 17
The region of M 17 has been imaged at 10.5 and 20.0 mr um with thegroundbased infrared camera MANIAC. In addition to a prominent diffuseemission bar (4\farcm5x0\farcm 3) extending southeast to northwest atthe interface between the H Ii region and the southwestern molecularcloud, the mosaic of 133 single frames at each wavelength revealed 22compact sources. One of these sources is the Kleinmann-Wright-Object andanother was previously identified as the ultra-compact H Ii region M17-UC1. Combining the N-band and Q-band data with near infrared datayielded spectral energy distributions that classifies all sources to beof Class I. The observed luminosities were between 55 and 4775 L_sun,which suggests that these sources represent the youngest generation ofmassive early type stars in M 17 and are surrounded by relics of theirprotostellar clouds. The morphology of the 10.5 and 20.0 mr um emissiontowards some of the sources reveals flattened structures and may be thefirst evidence of the presence of circumstellar disks around massivestars.
| On the Wilson-Bappu relationship in the Mg II k line
An investigation is carried out on the Wilson-Bappu effect in the Mg Iik line at 2796.34 Å. The work is based on a selection of 230 starsobserved by both the IUE and HIPPARCOS satellites, covering a wide rangeof spectral types (F to M) and absolute visual magnitudes (-5.4<=MV <=9.0). A semi-automatic procedure is used to measurethe line widths, which applies also in the presence of strong centralabsorption reversal. The Wilson-Bappu relationship here provided isconsidered to represent an improvement over previous recent results forthe considerably larger data sample used, as well as for a properconsideration of the measurement errors. No evidence has been found fora possible dependence of the WB effect on stellar metallicity andeffective temperature.
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
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Osservazione e dati astrometrici
| Costellazione: | Sagittario |
| Ascensione retta: | 18h27m58.20s |
| Declinazione: | -25°25'18.0" |
| Magnitudine apparente: | 2.81 |
| Distanza: | 23.697 parsec |
| Moto proprio RA: | -45.4 |
| Moto proprio Dec: | -186.8 |
| B-T magnitude: | 4.153 |
| V-T magnitude: | 2.924 |
Cataloghi e designazioni:
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NEWS@SKY (Science&Space News)
